From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Emanuel Berg via Users list for the GNU Emacs text editor Newsgroups: gmane.emacs.help Subject: Re: Is there a way of setting a variable only when it exists? Date: Tue, 15 Mar 2022 08:05:52 +0100 Message-ID: <8735jj4rvz.fsf@zoho.eu> References: <87lexdul8e.fsf@mbork.pl> <87lexcnq3w.fsf@web.de> <87bky7viz2.fsf@mbork.pl> Reply-To: Emanuel Berg Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="36615"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/29.0.50 (gnu/linux) To: help-gnu-emacs@gnu.org Cancel-Lock: sha1:mu8GcXg9yUG41ojDwWMjJE/012E= Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Tue Mar 15 16:39:25 2022 Return-path: Envelope-to: geh-help-gnu-emacs@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1nU9Gf-0009MP-4R for geh-help-gnu-emacs@m.gmane-mx.org; Tue, 15 Mar 2022 16:39:25 +0100 Original-Received: from localhost ([::1]:47320 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nU9Gd-0008GW-Np for geh-help-gnu-emacs@m.gmane-mx.org; Tue, 15 Mar 2022 11:39:23 -0400 Original-Received: from eggs.gnu.org ([209.51.188.92]:48724) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nU1Fz-0007xk-1V for help-gnu-emacs@gnu.org; Tue, 15 Mar 2022 03:06:11 -0400 Original-Received: from ciao.gmane.io ([116.202.254.214]:49500) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nU1Fu-0003SY-KP for help-gnu-emacs@gnu.org; Tue, 15 Mar 2022 03:06:10 -0400 Original-Received: from list by ciao.gmane.io with local (Exim 4.92) (envelope-from ) id 1nU1Fo-0008Kz-4R for help-gnu-emacs@gnu.org; Tue, 15 Mar 2022 08:06:00 +0100 X-Injected-Via-Gmane: http://gmane.org/ Mail-Followup-To: help-gnu-emacs@gnu.org Mail-Copies-To: never Received-SPF: pass client-ip=116.202.254.214; envelope-from=geh-help-gnu-emacs@m.gmane-mx.org; helo=ciao.gmane.io X-Spam_score_int: -16 X-Spam_score: -1.7 X-Spam_bar: - X-Spam_report: (-1.7 / 5.0 requ) BAYES_00=-1.9, HEADER_FROM_DIFFERENT_DOMAINS=0.249, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=no autolearn_force=no X-Spam_action: no action X-Mailman-Approved-At: Tue, 15 Mar 2022 11:35:41 -0400 X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Users list for the GNU Emacs text editor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Original-Sender: "help-gnu-emacs" Xref: news.gmane.io gmane.emacs.help:136583 Archived-At: Marcin Borkowski wrote: >>> so that `hello' is set to `"world"' if it is an existing >>> variable (e.g., defined by `defvar') and an error is >>> raised if `hello' does not exist. >> >> Byte compiling can help with things like name changes. > > Not necessarily. My use-case is an internal Emacs variable > I'm setting in my `init.el'; at the same time I submitted > a bug report/feature request to make it a user option, so > I assume that it might change its name in a future > Emacs version. If that variable change its name the byte-compiler will warn you since you will be shooting blanks. Here, try type: (setq no-such-var 'oh-la-la) then byte-compile, the byte-compiler will say: In toplevel form: geh.el:19:7: Warning: assignment to free variable ‘no-such-var’ BTW I wrote a program ages ago [1] and it tells me in 152 Elisp files just a small bunch of very few variables that I've ever used `setf' or `setq' on ;; .emacs.el, 204: show-paren-delay ;; erc-incal.el, 34: erc-user-full-name ;; erc-incal.el, 77: erc-header-line-format ;; spell.el, 17: ispell-program-name ;; w3m-incal.el, 26: w3m-tab-width are actually options. I don't remember anymore why that was important to know? I didn't like custom or options back then (and still don't) so maybe an attitude/political thing but ... yeah, what? [1] https://dataswamp.org/~incal/emacs-init/custom-vars.el -- underground experts united https://dataswamp.org/~incal